The melanocortin receptors (MCR), MC3R and MC4R, have established roles in feeding and pituitary function. MC5R mRNA expression has been identified at low levels in the hypothalamus. However, a role for this receptor in appetite and pituitary function remains to be elucidated. We investigated the effects of central administration of an MC5R agonist (3,3,3-triphenylpropionyl-His-D-Phe-Arg-Trp-NH2) on food intake and plasma pituitary hormone levels. We did not observe any alteration in feeding following injection of the MC5R agonist at doses up to 1 nmol, into the third ventricle or paraventricular nucleus of the hypothalamus in satiated or 24 hour fasted male Wistar rats. Additionally, there was no alteration in thyroid stimulating hormone, leutinising hormone, growth hormone, prolactin, adrenocorticotrophic hormone or corticosterone plasma levels at either 20 or 40 minutes post-injection of 1 nmol MC5R agonist into the third ventricle of satiated male Wistar rats. Thus, our results suggest that, unlike the MC3R and MC4R, the MC5R does not play an important role in feeding regulation and pituitary function.
22 - 24 Mar 2004
British Endocrine Societies